Recently, an optical disk, such as a CD (Compact Disc) or a DVD (Digital Versatile Disk), on which a user can record information, so-called a write-once optical disk, is widely used. Such optical disk is provided with, for example, as disclosed in Patent Document 1, an information recording layer that is an optical absorption layer made of dye, and information is recorded by irradiating recording light to the information recording layer, then decomposing dye in an area irradiated with the light, and forming a recording mark.    Patent Document 1: Japanese Patent Application Laid-Open No. H6-103611